Airworthiness directives: how to track them and prove compliance

Airworthiness directives exist because the regulator found an unsafe condition in a design and decided owners must correct it. Unlike a manufacturer's service bulletin, an AD is not a suggestion once it applies to your aircraft: it is law, with its own deadlines and its own required wording.

How an AD finds your aircraft

• Applicability is usually by model and serial number range, so two identical aircraft can have different AD lists.
• ADs apply to components installed on the aircraft too — engine, propeller, seats, brakes, radios — not only to the airframe.
• Some ADs are one-time and terminate when done; others repeat on a calendar or an hour interval forever.
• Many ADs say 'unless already embodied', which means earlier compliance during production or a prior modification can count — but only if it is documented.
• An AD can require interim measures: inspect every so many hours, reduce weight, restrict speed, or placard something.

Where to check

1. 1Search the airworthiness directives of the authority of the state of registry, by make, model and serial number.
2. 2Do the same for the engine, the propeller and any major component with its own type certificate.
3. 3Subscribe to alerts for your aircraft type so a new AD reaches you instead of reaching your mechanic at the next annual.
4. 4When you buy an aircraft, treat the AD search as part of the pre-buy — it is far cheaper to learn about an AD before you own the airplane.

What a compliance record must show

• The AD number, including the revision or amendment you complied with.
• The method used, in the AD's own terms — many ADs allow several methods and the record must say which one you used.
• The date of compliance and the aircraft, engine and propeller times or cycles at that moment.
• The serial number of the affected component, when the AD applies to a part rather than the whole aircraft.
• The signature and certificate number of the person who performed or supervised the work.
• For recurring ADs, the next due date or due time. For one-time ADs, a clear statement that compliance is terminated.

How to keep track

Keep one compliance table per aircraft. A workable table has one row per AD and these columns: AD number, what it applies to (airframe, engine, propeller or component with serial), method used, compliance date and times, next due, and where the evidence is filed. Then do three things with it: update it the day the work is done, review it with your mechanic before every inspection, and hand it to the next owner at closing.

What happens when one slips

• An aircraft with an overdue AD is not in compliance and should not fly, the same as one with an expired annual.
• The fix can be small — an inspection, a placard, a bolt replacement — or it can require replacing a component.
• At sale time an AD gap stops deals: the buyer's mechanic finds it, and the negotiation restarts from there.
• The compliance history belongs to the aircraft and must be transferred with it, so never let it stay in a shop drawer.